Patient-controlled analgesia techniques have opened a new dimension to individualize patient's need for analgesia, in the treatment of acute post-operative pain. These techniques can be used intravenously, in the epidural space, and into peripheral nerve sheets. There is a common consensus that intravenous patient-controlled analgesia should not have a continuous infusion while epidural patient-controlled analgesia (PCEA) should be programmed with a continuous infusion. The drugs used for epidural analgesia are: opioids, local anaesthetics or the combination of both. The combinations seem to provide better pain relief and less side effects. The continuous epidural infusion of opioids has the advantages of fewer fluctuations in cerebrospinal fluid concentrations of drug, but it is necessary to administer a loading bolus, to overcome the fact that it takes several hours to provide adequate analgesia. The advantages of epidural versus intravenous patient-controlled analgesia are represented by better analgesia and a reduced opioids requirement, while the advantages when compared to epidural continuous infusion are: increased efficiency, self-adjustment by the patient, higher patient satisfaction, less sedation, and lower opioids dosage. The clinical advantages of PCEA may outweigh the greater cost and invasiveness of this technique.